This issue rises normally when a new domain is added to existing WordPress website with a different domain name. For example the WordPress database and files were previously connected to google.com and after transferring the contents to new domain facebook.com the site kit is still connected to google.com.
How to solve ‘redirect_uri’ mismatch issue
Add domain name as property in search console. If purchased from GoDaddy add a text as provided from search console in TXT record in DNS of domain.
Enable google analytics in Google Cloud Console
Go to WordPress dashboard and click on Site Kit settings. Now click on Admin Settings. Now click on reset site kit.
Disable all the plugins installed in the WordPress other than site kit. There is no need to delete the plugins. Disabling the plugin is more than enough to solve the issue.
Now visit site kit settings in WordPress dashboard and click on CONNECT google analytics. Add it as new property in WP setting of site kit. Earlier it would have shown redirect_uri’ mismatch when connection is attempted. But now it will be redirected to the Gmail account. Now select the Gmail account associated with google analytics.
While logging in permission to create subsection in Google Analytics will be asked by gmail.com. Tick that option and continue logging in to Gmail account. Now message will be displayed as your Site Kit is successfully connected in WP dashboard. You can enable all the previously disabled plugins now.